Internet protocol (IP) multicast is an Internet standard that enables bandwidth-efficient distribution of video, audio and other data through a network. IP multicast packets are addressed to a group address rather than to a destination IP address such as in a traditional point-to-point communication. The network path that such packets take as they are routed through the network forms a distribution tree.
At the edge of the network, traffic for a multicast group is discarded unless one or more local user devices have joined the group. A user device joins the group by issuing a join request which is automatically processed by the edge device. The edge device then forwards multicast traffic for the group to the user.
The advantage of IP multicast is that even when there are multiple users interested in receiving the same data, only a single copy of the data travels through the backbone network to the network edge. At the edge, the date is replicated and separately transmitted to the users.
IP multicast, however, is geared toward enterprise or corporate networks that permit anyone to join a multicast group. Thus, any user on the network is able to receive multicast traffic as long as that data is available on the network. As a result, service provider networks cannot use IP multicast to distribute premium services.